1. Field of the Invention
The present invention relates to a teaching apparatus for teaching data with reference to a working point to such as an industrial robot, more particularly to a teaching apparatus which is improved in safety.
2. Discussion of the Background
As a conventional zeaching method for teaching data of a working point to an industrial robot, there is a direct teaching method, as disclosed in J.P.A. Gazette 85106/1981, in which a force sensor is provide as a teaching tool in a manual operation part of the industrial robot, each driving unit for driving an industrial robot is controlled according to directives showing positional data of a tip and attitude data of a wrist of the robot which are indicated by signals generated by the force sensor at the time when an operator operates the manual operation part to lead the position of the tip and the attitude of the wrist of the robot, and thus the data (lead data) controlling each driving unit are stored in a memory.
Further, in a method disclosed in J.P.A. Gazette 71086/1983, teaching tool 221 having a built-in force sensor is attached to the tip of robot 211 as shown in FIG. 1, and force control is performed corresponding to the force or the moment which is applied to teaching tool 221, when operator 214 directly manipulates teaching tool 221, and thus the position or the speed of the robot is controlled for leading a working tool of the robot. When performing teaching, operator 214 instructs the start and termination of teaching by manipulating many switches provided in teaching tool 221.
Different from the direct teaching method as above, there is an indirect teaching method as shown in FIG. 2, in which operator 214 manipulates teaching manipulator 220 provided with manipulation switches for teaching the motion of the robot to lead robot 211.
Conventional examples shown in FIG. 1 and FIG. 2 each shows the same example in which cylindrical tube 213 is welded on a flat plate.
Among the conventional examples shown above, the method disclosed in J.P.A. Gazette 85106/1981 has a risk such that, if the operator stumbles during teaching and leads the teaching tool with excessive foe or makes the teaching tool contact the work or other obstruction, excess force is applied to a force detector and then abrupt motion of the robot is caused due to the excessive torque thus generated.
Or, in case the operator is caught between the arms of the robot or between the arm and the work while he is leading a teaching tool and the robot is generating power in the direction of applying force to the operator standing therebetween, it is hard for the operator to escape from this state.
Further, even when the operator detects danger during direct teaching, he will be unable to avoid the danger because he has no means at hand to suddenly stop the motion of the robot.
Still further, when the output from the force detector varies due to a temperature drift or external force is applied to the force detector, a teaching handle is not in a fixed position and there is a danger that a robot may move contrary to the operator's intention. Also when a working tool makes contact during direct teaching operation with the work or other obstruction, there is a danger that the robot may continue to move deforming the working tool. Moreover, when the operator performs the teaching of a narrow portion of the work, the teaching handle on the working tool becomes an obstrution, thereby causing a danger that the operator's arm may be grasped by the work, and further that the robot may be locked at the time of emergency stop, and in the worst case, the operator may be held in a constrained state being unable to escape therefrom.
With the robot shown in FIG. 1, since the operator performs teaching while manipulating many switches on the teaching tool for leading the robot, the physical/mental fatigue of the operator becomes very large. Further, when one teaching tool is commonly used among a plurality of robots, it becomes necessary to lay the wiring from the teaching tool to respective robot controllers directly thereby requiring a large cost.
Also as for the robot shown in FIG. 2, since the operator leads the robot per each axis or leads in the XYZ direction on the robot coordinate system or on the tool coordinate system through manipulation switches on a teaching manipulator, it is hard to intuitively lead the position or the attitude of the robot or the tool relative to the work, and the large physical/mental fatigue of the operator as well as the prolonged teaching time are required, causing a disadvantage to the person concerned.